Optical switch is one of the essential components of an all-optical network for performing a direct, cross, and multi-way switching transmission of optical signals in an optical fiber network system. In the past, a widely used optical switch generally converted an inputted optical signal into an electric signal, and then switched the path of the electric signal, and finally converted the electric signal into another optical signal coupled to the optical fiber. This method is complicated and power-consuming, and thus it is not advantageous for the future development and popularity of the all-optical network system.
The optical switch can be divided mainly into the following types: a mechanical optical switch (including a prism type, a MEMS type, and a fiber type), an optoelectronic optical switch, a liquid crystal optical switch, an optothermal optical switch, a magnetic optical switch and an acoustic optical switch according to the operating principle. Although there are various different models of optical switches, yet most of the optical switches used in the all-optical network are mechanical optical switches, and optical switch becomes a mainstream in the market of optical communication components.
The mechanical optical switch uses an actuator which is a mechanical component such as a comb drive, a motor, and a cam having a motive force to drive a micro mirror (MEMS type), an optical fiber (fiber type, optical fiber to optical fiber type) or a prism (prism type) for switching the optical path. The weights of these applications are 7% for the MEMS type, 9% for the optical fiber type, and 84% for the prism type.
Many different models of 2×2 mechanical optical switches have been disclosed in the prior arts, but a vast majority of these switches are manufactured by an all-MEMS process. Since the dimensions of the optical switch manufactured by the all-MEMS process are very small, it is necessary to use a lens fiber (such as ball-lens fiber or taper lens fiber) for the assembling, and thus these switches incur a higher manufacturing cost, a very short working distance (approximately 100 microns to 300 microns), and a very serious lateral misalignment sensitivity. For instance, a lens fiber such as a ball-lens fiber is used for assembling and alignment, which usually causes a misalignment of 1 μm and an optical loss of 1˜2 dB.
As to a prior art that employs a 2×2 mechanical optical switch for the micro mirror, the 2×2 optical switch as disclosed in U.S. Pat. No. 6,819,809 installs a micro mirror device at a torque rod and applies a voltage to an electrode disposed adjacent to the mirror, and electric charges drive the micro mirror to rotate, so as to change the optical transmission. The optical switch disclosed in U.S. Pat. No. 6,711,321 installs a micro mirror at a cantilever beam and controls an electromagnetic force to attract the cantilever beam to set the operating position of the micro mirror.
The 2×2 mechanical optical switch manufactured by the foregoing method achieves the functions of the 2×2 optical switch, but the thickness of the micro mirror produced in the micro mirror manufacturing process affects the alignment precision, and thus it is necessary to use a precise control mechanism to avoid optical loss due to inaccurate alignment. However, a high precision control mechanism has the disadvantages of high cost and poor long-time stability, so that a high precision control mechanism is not advantageous to product commercialization and market competitiveness.
Therefore, developing a 2×2 mechanical optical switch with an easy automatic manufacture and alignment to lower the manufacturing cost of the optical switch and increase the long-time stability becomes an important subject for manufacturers and an objective of the present invention.